Upper West Sider Aaron Harris, the 26-year-old CEO of tech start-up Tutorspree, escaped the snowy Big Apple last month for a stint in Silicon Valley — where it’s been raining money since he got there.

Harris and his partners — fellow Upper West Side resident Josh Abrams, 27, and 25-year-old Ryan Bednar, of Jersey City — are one group of 43 companies lucky enough to be chosen to take part in a tech incubator program called Y Combinator — which forks over $20,000 for a stake in the company of between 2 percent and 10 percent.

But when Harris, Abrams and Bednar arrived on the West Coast, they learned that Russian super-investor Yuri Milner — of Facebook and Twitter investment fame — and mega-dealmaker Ron Conway had decided to invest an additional $150,000 in each of the 43 start-ups.

It was a late Christmas present tech wannabe moguls dream of.

The three partners are living in a rented house for three months and are being mentored before deciding if they want to return East or remain in Silicon Valley to try to grow their New York-born company, which links parents with private educators for their children.

The money from Y Combinator was supposed to be all they would live on — until Milner and Conway came along.

“The investment will increase our ability to rapidly improve Tutorspree,” Harris told The Post last week. “It doesn’t really change how much capital we’re going to raise, but it does give us a head start on raising it.”

Milner and Conway made their investment through a new vehicle called the Start Fund, whose stake in each of the companies will be based on later-stage funding. The Start Fund asked no questions before handing over the cash — relying totally on YC’s expertise.

It’s a style of investment that Silicon Valley insiders say has never been done before.

Not everyone in Silicon Valley likes Milner’s style, however.

Funding early-stage start-ups is usually more precise than this shotgun method. Angel investors normally scrutinize their deals.

Milner’s strategy, coming in the midst of a tech rally, is more like investing in an index fund — after all, in this run-up in technology, one of the 43 is likely to succeed and return a bountiful yield to the fund.

One angel investor, who has spent decades in Silicon Valley, told The Post that the Milner deal sends the wrong message to younger investors.

“There’s a generation of investors who came into the business world just as the dot-com bubble was starting, so their only point of reference about a good economic up-time was this style of undisciplined investing,” said the founder of one of Silicon Valley’s top angel firms.

Sour grapes are what Milner supporters are saying of the critics.

“A lot of angels feel Ron and Yuri stole the sandwich out of their mouth,” said Paul Graham, who runs Y Combinator. “They swooped in and invested in everybody first.”